docs: def is_in_bounds(self, x):
          """not yet tested"""
          if self.bounds is None:
              return True
          for ib in [0, 1]:
              if self.bounds[ib] is None:
                  continue
              for i in rglen(x):
                  idx = min([i, len(self.bounds[ib]) - 1])
                  if self.bounds[ib][idx] is not None and \
                          (-1)**ib * x[i] < (-1)**ib * self.bounds[ib][idx]:
                      return False
          return True